The present invention relates to security systems with devices for detecting the location of an object between one and a plurality of different locations. More specifically, the present invention relates to security systems with infrared devices for detecting an open door or window, and to wireless security systems utilizing such devices.
Security systems presently known to the art detect open doors or windows in a number of ways. Hard wire systems generally utilize magnetic switches having mating parts mounted on and adjacent to a door or window which separate when the door is open, thereby actuating the alarm. Such hard wire systems require careful installation and are costly to install. Another type of device for detecting the opening of a door is an ultrasonic unit in which ultrasonic energy is made to impinge upon the door and the reflected energy utilized to indicate a closed door condition. Ultrasonic systems have been sensitive to temperature changes and external noise, and often have been difficult to install so as to avoid false triggering. Infrared detectors have been utilized to detect the presence of a warm body passing through an open door, or a change in temperature caused by the opening of a door. The presence of ambient light or heat have tended to make such systems unreliable.